NEW YORK (CNNMoney.com) -- Gasoline prices declined for the 70th straight day, falling below the $1.87 per gallon mark, according to a national survey of credit card swipes at gasoline stations.

The national average fell 1.7 cents, sinking to the lowest level since Jan. 27, 2005, according to motorist group AAA. Over the last 70 days gas prices have plummeted 52%.

Prices at the pump have dropped $1.223 per gallon from a year ago and are now down 55% from the record-high of $4.114 per gallon reached in mid-July.

A total of 38 states recorded prices below $2 a gallon, with the cheapest gas found in Missouri, where prices averaged $1.571 a gallon.

Alaska continued to have the highest price at $2.889 per gallon.

2008: A volatile year for gas

Prices at the pump have been on a rollercoaster in 2008. Soaring prices curtailed travel this summer, and Americans waited months for a reprieve. They cut back spending in order to fill their gas tanks.

When the price reached the record-high $4.114 a gallon set on July 17, gas prices had risen already 35% year-over-year.

Gas prices finally began to sink on Aug. 21, as the dollar strengthened and oil prices saw their biggest drop in 17 years.

Late August brought Hurricane Gustav threatening infrastructure in the Gulf of Mexico. The storm shut down nearly all crude oil production and 82% of natural gas production in the Gulf region. Soon after, Hurricane Ike loomed over Texas and gas prices shot up in September, reaching more than $5 per gallon in some parts of the country during the early part of the month.